evident (fig. 9). If this inaccurate representation 

 is carried over into the surface current field en- 

 tered into the computer array for iceberg drift, 

 the surface current velocity component calculated 

 from that field would tend to bias the drift in 

 cross slope direction resulting in a biased iceberg 

 drift prediction. 



The obvious solution to this problem is to en- 

 sure that all isosteric surfaces below the ocean 

 bottom in stations shallower than the reference 

 level are level, and to show no slope resulting 

 in current into or out of the Bank. However, 

 to do this, a single set of averaged extrapolated 

 values would have to be applied to all the shallow 

 stations. This would give erroneous data for 

 current estimates for the component of flow 

 parallel to the Bank computed for continental 

 slope stations of a magnitude equal to or greater 

 than the eiTor due to varying the extrapolated 

 values from section to section. 



There appears to be no solution to this problem 

 that would preserve the relative dynamic to- 

 pography from one station to the next and from 

 one section to the next while still giving an 

 accurate indication of flow up and down slope, 

 if any. Procedurally in the course of perform- 

 ing computer drift predictions the effects of the 

 bias upon drift caused by unrealistic flow in a 

 direction normal to the Bank may be removed 



if the magnitude can be estimated. This is 

 simply done by calculating the surface current 

 from dynamic height differences between adjacent 

 sections (i.e., normal to the slope) using the 

 deepest common depth of the two shallowest end 

 stations of each section as the reference level for 

 computing the dynamic height of the water 

 column above that level (fig. 10). By setting 

 the flow at this reference level to zero, one estab- 

 lishes mathematically what is known intuitively, 

 that no current exists below the sediment bound- 

 ary layer of the Bank. 



Now that the cross slope component of cur- 

 rent velocity has been determined independently 

 of the along slope flow it may be applied to the 

 iceberg drift solution in several ways. The east 

 and north component of flow could be summed 

 to obtain a current velocity vector applied in the 

 vicinity of the western end of the sections con- 

 cerned. Alternatively, the current velocities cal- 

 culated for the cross slope flow in the manner 

 described above might be programmed to com- 

 pute the maximum allowable component of up- 

 slope-downslope force for the computer solution 

 of iceberg drift. Either application should im- 

 prove the estimated current velocity input to 

 predicted drift of icebergs when they are found 

 in water shallower than 1000 meters. 



11 



